The actual number of important sulfhydryl groups in E. coli succinic thiokinase and the subunit loci (alpha or beta chain) will be determined. Peptides containing the active sulfhydryl groups or their derivatives will be purified to homogeneity and sequenced. The possibility that lysyl epsilon-amino groups may be involved in coenzyme A and ATP binding will be examined. Cross-linking of peptides will be employed to ascertain the relationship of alpha and beta chains at the "active site." The succinate binding site of allosteric acetate kinase will be examined in the light of its possible similarity to that in succinic thiokinase. BIBLIOGRAPHIC REFERENCES: Nishimura, J.S., Kenyon, G.L., and Smith, D.J. (l975) Reversible modification of the sulfhydryl groups of Escherichia coli succinic thiokinase with methanethiolating reagents, 5,5'-dithiobis (2-nitrobenzoic acid), p-hydroxymercuribenzoate and ethylmercurithiosalicylate. Arch. Biochem. Biophys. l70, 46l-467. Nishimura, J.S., Mitchell, T., and Matula, J.M. (l976) Inactivation of Escherichia coli succinic thiokinase by selective oxidation of thiol groups by permanganate. Biochem. Biophys. Res. Commun. 69, 1057-1064.